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What Is The Functional Group Of An Aldehyde And Ketone?

Aldehydes And Ketones

Aldehydes And Ketones

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Reactions Of Aldehydes And Ketones

Reactions Of Aldehydes And Ketones

Aldehydes and ketones undergo a variety of reactions that lead to many different products. The most common reactions are nucleophilic addition reactions, which lead to the formation of alcohols, alkenes, diols, cyanohydrins (RCH(OH)C&tbond;N), and imines R 2C&dbond;NR), to mention a few representative examples. The main reactions of the carbonyl group are nucleophilic additions to the carbon‐oxygen double bond. As shown below, this addition consists of adding a nucleophile and a hydrogen across the carbon‐oxygen double bond. Due to differences in electronegativities, the carbonyl group is polarized. The carbon atom has a partial positive charge, and the oxygen atom has a partially negative charge. Aldehydes are usually more reactive toward nucleophilic substitutions than ketones because of both steric and electronic effects. In aldehydes, the relatively small hydrogen atom is attached to one side of the carbonyl group, while a larger R group is affixed to the other side. In ketones, however, R groups are attached to both sides of the carbonyl group. Thus, steric hindrance is less in aldehydes than in ketones. Electronically, aldehydes have only one R group to supply electrons toward the partially positive carbonyl carbon, while ketones have two electron‐supplying groups attached to the carbonyl carbon. The greater amount of electrons being supplied to the carbonyl carbon, the less the partial positive charge on this atom and the weaker it will become as a nucleus. The addition of water to an aldehyde results in the formation of a hydrate. The formation of a hydrate proceeds via a nucleophilic addition mechanism. 1. Water, acting as a nucleophile, is attracted to the partially positive carbon of the carbonyl group, generating an oxonium ion. Acetal formation reacti Continue reading >>

Organic Chemistry/ketones And Aldehydes

Organic Chemistry/ketones And Aldehydes

Aldehydes () and ketones () are both carbonyl compounds. They are organic compounds in which the carbonyl carbon is connected to C or H atoms on either side. An aldehyde has one or both vacancies of the carbonyl carbon satisfied by a H atom, while a ketone has both its vacancies satisfied by carbon. 3 Preparing Aldehydes and Ketones Ketones are named by replacing the -e in the alkane name with -one. The carbon chain is numbered so that the ketone carbon, called the carbonyl group, gets the lowest number. For example, would be named 2-butanone because the root structure is butane and the ketone group is on the number two carbon. Alternatively, functional class nomenclature of ketones is also recognized by IUPAC, which is done by naming the substituents attached to the carbonyl group in alphabetical order, ending with the word ketone. The above example of 2-butanone can also be named ethyl methyl ketone using this method. If two ketone groups are on the same structure, the ending -dione would be added to the alkane name, such as heptane-2,5-dione. Aldehydes replace the -e ending of an alkane with -al for an aldehyde. Since an aldehyde is always at the carbon that is numbered one, a number designation is not needed. For example, the aldehyde of pentane would simply be pentanal. The -CH=O group of aldehydes is known as a formyl group. When a formyl group is attached to a ring, the ring name is followed by the suffix "carbaldehyde". For example, a hexane ring with a formyl group is named cyclohexanecarbaldehyde. Aldehyde and ketone polarity is characterized by the high dipole moments of their carbonyl group, which makes them rather polar molecules. They are more polar than alkenes and ethers, though because they lack hydrogen, they cannot participate in hydrogen bonding like Continue reading >>

Ketone

Ketone

Not to be confused with ketone bodies. Ketone group Acetone In chemistry, a ketone (alkanone) /ˈkiːtoʊn/ is an organic compound with the structure RC(=O)R', where R and R' can be a variety of carbon-containing substituents. Ketones and aldehydes are simple compounds that contain a carbonyl group (a carbon-oxygen double bond). They are considered "simple" because they do not have reactive groups like −OH or −Cl attached directly to the carbon atom in the carbonyl group, as in carboxylic acids containing −COOH.[1] Many ketones are known and many are of great importance in industry and in biology. Examples include many sugars (ketoses) and the industrial solvent acetone, which is the smallest ketone. Nomenclature and etymology[edit] The word ketone is derived from Aketon, an old German word for acetone.[2][3] According to the rules of IUPAC nomenclature, ketones are named by changing the suffix -ane of the parent alkane to -anone. The position of the carbonyl group is usually denoted by a number. For the most important ketones, however, traditional nonsystematic names are still generally used, for example acetone and benzophenone. These nonsystematic names are considered retained IUPAC names,[4] although some introductory chemistry textbooks use systematic names such as "2-propanone" or "propan-2-one" for the simplest ketone (CH3−CO−CH3) instead of "acetone". The common names of ketones are obtained by writing separately the names of the two alkyl groups attached to the carbonyl group, followed by "ketone" as a separate word. The names of the alkyl groups are written alphabetically. When the two alkyl groups are the same, the prefix di- is added before the name of alkyl group. The positions of other groups are indicated by Greek letters, the α-carbon being th Continue reading >>

Protecting Groups In Grignard Reactions

Protecting Groups In Grignard Reactions

Now that we’ve gone over the most useful reactions of Grignard reagents – addition to epoxides, aldehydes, ketones, and esters – let’s go back to the topic of how to make Grignard reagents, albeit with a twist. Here’s the summary for today’s post: Introducing Yet Another Way To Royally Screw Up Making A Grignard Reagent In a previous post we said that there are cases where making Grignard reagents can fail due to the presence of an acidic proton. Like this example. The problem here is that Grignard reagents are strong bases, and will react with even weak acids (like alcohols). If we try to make a Grignard on a molecule with an acidic functional group, we’ll end up destroying our Grignard instead. We saw that one way around this problem was to protect alcohols as some kind of inert functional group (like an ether) which doesn’t react with our Grignard. Similarly, there are other cases of molecules where making a Grignard reagent will fail for similar reasons. For example: why does this reaction not give the desired Grignard reagent? The problem here, as you might have guessed if you read the last post, is that this Grignard reagent reacts with itself!!! Once formed, the Grignard would react with the ketone from the starting material. This could then react with Mg to give a new Grignard, which would react with more ketone… and so on. The result is a mess. “Protecting Groups” Mask A Functional Group From Attack If we were able to find some way to “mask” the ketone in this case, possibly as some unreactive functional group that is completely inert to Grignard reagents, then we could then make the Grignard reagent without causing any problems of self-reactivity. Then, once we’re done, we could then “unmask” the protecting or masking group, rev Continue reading >>

Chapter 5 Aldehydes And Ketones

Chapter 5 Aldehydes And Ketones

5.1 Introduction H Aldehydes have a -C=O functional group. An aldehyde requires that at least one of the bonds on the C=O group is a hydrogen atom. When the carbonyl group (C=O) has two C atoms bonded to it is classified as a ketone. 5.2 Naming Aldehydes and Ketones Systematic: methanal ethanal propanal butanal Common: formaldehyde acetaldehyde You should know the common names! They are more commonly used than the systematic names. Ketones: Systematic: propanone 1,3-dihydroxypropanone 3-heptanone Common: acetone dihydroxyacetone(DHA) The ketone is assigned a number on the chain starting from whichever end gives the smaller number. It takes priority over branches off the chain. Methanal (formaldehyde) is a commonly used preservative for biological specimens although concern about it being a mild carcinogen has prompted efforts to reduce its use and to provide very good ventilation when it is used to minimize exposure. Propanone (acetone) is commonly used in nail polish remover. It is also a metabolic product sometimes formed by diabetics who are not controlling their blood sugar. It is readily detected, because it makes the breath smell like nail polish remover or “fruityâ€, not a normal situation! This condition is called ketosis, indicating the presence of ketones in the blood. This condition is also commonly associated with blood acidosis and the combined condition is referred to as ketoacidosis. Dihydroxyacetone is the active ingredient in some sunless sun tanning lotions. It reacts with amino acids in the skin to form melaninoids which have a brown color. In its original formulation, it gave an orange tan but improvements in formulations have improved its esthetics considerably. It absorbs primarily in the UV-A range (320-400 nm) but only with a typical SPF Continue reading >>

Reactions Of Aldehydes And Ketones

Reactions Of Aldehydes And Ketones

Reference: McMurry Ch 9 George et al Ch 2.6 Structure and bonding Contain a carbonyl group, C=O Aldehydes have at least one H attached to the carbonyl group, ketones have two carbon groups attached to the carbonyl group Carbon of the carbonyl group is sp2 hybridised The C=O bond is polar Aldehydes and ketones strongly absorb radiation around ~ 1700 cm-1 in the infrared region Nomenclature Aldehydes The longest chain containing the CHO group gives the stem; ending �al If substituents are present, start the numbering from the aldehyde group - C1 Ketones The longest chain containing the carbonyl group gives the stem; ending �one If substituents are present number from the end of the chain so the carbonyl group has the lowest possible number There are non-systematic names for the common aldehydes and ketones With the exception of oxidation of aldehydes, the reactions of aldehydes and ketones is dominated by nucleophilic addition. 1. Oxidation of aldehydes Aldehydes (but not ketones) may be oxidised to carboxylic acids with Cr2O72- / H+ Example: 2. Nucleophilic addition The double bond of the carbonyl group undergoes an addition reaction The polarity of the C=O bond results in the addition of a nucleophile (Nu-) to the carbon atom, breaking of the double bond and addition of H+ to the oxygen is always the second step and results in an alcohol Common nucleophiles include the Grignard reagent (RMgX), hydride ion (H- from LiAlH4 or NaBH4) In summary Examples: Grignard reaction Recap � generation of a Grignard reagent from an alkyl halide and magnesium in dry diethyl ether solvent Grignard reagents also react with carbon dioxide to generate carboxylic acids after addition of aqueous H+ Reduction Reduction of the non-polar C=C or C� C bonds in alkenes and alkynes respecti Continue reading >>

Introducing Aldehydes And Ketones

Introducing Aldehydes And Ketones

This page explains what aldehydes and ketones are, and looks at the way their bonding affects their reactivity. It also considers their simple physical properties such as solubility and boiling points. Details of the chemical reactions of aldehydes and ketones are described on separate pages. What are aldehydes and ketones? Aldehydes and ketones as carbonyl compounds Aldehydes and ketones are simple compounds which contain a carbonyl group - a carbon-oxygen double bond. They are simple in the sense that they don't have other reactive groups like -OH or -Cl attached directly to the carbon atom in the carbonyl group - as you might find, for example, in carboxylic acids containing -COOH. Examples of aldehydes In aldehydes, the carbonyl group has a hydrogen atom attached to it together with either a second hydrogen atom or, more commonly, a hydrocarbon group which might be an alkyl group or one containing a benzene ring. For the purposes of this section, we shall ignore those containing benzene rings. Note: There is no very significant reason for this. It is just that if you are fairly new to organic chemistry you might not have come across any compounds with benzene rings in them yet. I'm just trying to avoid adding to your confusion! Notice that these all have exactly the same end to the molecule. All that differs is the complexity of the other group attached. When you are writing formulae for these, the aldehyde group (the carbonyl group with the hydrogen atom attached) is always written as -CHO - never as COH. That could easily be confused with an alcohol. Ethanal, for example, is written as CH3CHO; methanal as HCHO. The name counts the total number of carbon atoms in the longest chain - including the one in the carbonyl group. If you have side groups attached to the ch Continue reading >>

Chapter 16: Aldehydes And Ketones (carbonyl Compounds)

Chapter 16: Aldehydes And Ketones (carbonyl Compounds)

The Carbonyl Double Bond Both the carbon and oxygen atoms are hybridized sp2, so the system is planar. The three oxygen sp2 AO’s are involved as follows: The two unshared electorn pairs of oxygen occupy two of these AO’s, and the third is involved in sigma bond formation to the carbonyl carbon. The three sp2 AO’s on the carbonyl carbon are involved as follows: One of them is involved in sigma bonding to one of the oxygen sp2 AO’s, and the other two are involved in bonding to the R substituents. The 2pz AO’s on oxygen and the carbonyl carbon are involved in pi overlap, forming a pi bond. The pi BMO, formed by positive overlap of the 2p orbitals, has a larger concentration of electron density on oxygen than carbon, because the electrons in this orbital are drawn to the more electronegative atom, where they are more highly stabilized. This result is reversed in the vacant antibonding MO. As a consequence of the distribution in the BMO, the pi bond (as is the case also with the sigma bond) is highly polar, with the negative end of the dipole on oxygen and the positive end on carbon. We will see that this polarity, which is absent in a carbon-carbon pi bond, has the effect of strongly stabilizing the C=O moiety. Resonance Treatment of the Carbonyl Pi Bond 1.Note that the ionic structure (the one on the right side) has one less covalent bond, but this latter is replaced with an ionic bond (electrostatic bond). 2.This structure is a relatively “good” one, therefore, and contributes extensively to the resonance hybrid, making this bond much more thermodynamically stable than the C=C pi bond, for which the corresponding ionic structure is much less favorable (negative charge is less stable on carbon than on oxygen). 3.The carbonyl carbon therefore has extensive car Continue reading >>

Aldehydes, Ketones, Carboxylic Acids, And Esters

Aldehydes, Ketones, Carboxylic Acids, And Esters

Learning Objectives By the end of this section, you will be able to: Describe the structure and properties of aldehydes, ketones, carboxylic acids and esters Another class of organic molecules contains a carbon atom connected to an oxygen atom by a double bond, commonly called a carbonyl group. The trigonal planar carbon in the carbonyl group can attach to two other substituents leading to several subfamilies (aldehydes, ketones, carboxylic acids and esters) described in this section. Aldehydes and Ketones Both aldehydes and ketones contain a carbonyl group, a functional group with a carbon-oxygen double bond. The names for aldehyde and ketone compounds are derived using similar nomenclature rules as for alkanes and alcohols, and include the class-identifying suffixes –al and –one, respectively: In an aldehyde, the carbonyl group is bonded to at least one hydrogen atom. In a ketone, the carbonyl group is bonded to two carbon atoms: In both aldehydes and ketones, the geometry around the carbon atom in the carbonyl group is trigonal planar; the carbon atom exhibits sp2 hybridization. Two of the sp2 orbitals on the carbon atom in the carbonyl group are used to form σ bonds to the other carbon or hydrogen atoms in a molecule. The remaining sp2 hybrid orbital forms a σ bond to the oxygen atom. The unhybridized p orbital on the carbon atom in the carbonyl group overlaps a p orbital on the oxygen atom to form the π bond in the double bond. Like the C=O bond in carbon dioxide, the C=O bond of a carbonyl group is polar (recall that oxygen is significantly more electronegative than carbon, and the shared electrons are pulled toward the oxygen atom and away from the carbon atom). Many of the reactions of aldehydes and ketones start with the reaction between a Lewis base and Continue reading >>

Nomenclature Of Aldehydes & Ketones

Nomenclature Of Aldehydes & Ketones

Aldehydes and ketones contain the carbonyl group. Aldehydes are considered the most important functional group. They are often called the formyl or methanoyl group. Aldehydes derive their name from the dehydration of alcohols. Aldehydes contain the carbonyl group bonded to at least one hydrogen atom. Ketones contain the carbonyl group bonded to two carbon atoms. Aldehydes and ketones are organic compounds which incorporate a carbonyl functional group, C=O. The carbon atom of this group has two remaining bonds that may be occupied by hydrogen, alkyl or aryl substituents. If at least one of these substituents is hydrogen, the compound is an aldehyde. If neither is hydrogen, the compound is a ketone. Naming Aldehydes The IUPAC system of nomenclature assigns a characteristic suffix -al to aldehydes. For example, H2C=O is methanal, more commonly called formaldehyde. Since an aldehyde carbonyl group must always lie at the end of a carbon chain, it is always is given the #1 location position in numbering and it is not necessary to include it in the name. There are several simple carbonyl containing compounds which have common names which are retained by IUPAC. Also, there is a common method for naming aldehydes and ketones. For aldehydes common parent chain names, similar to those used for carboxylic acids, are used and the suffix –aldehyde is added to the end. In common names of aldehydes, carbon atoms near the carbonyl group are often designated by Greek letters. The atom adjacent to the carbonyl function is alpha, the next removed is beta and so on. If the aldehyde moiety (-CHO) is attached to a ring the suffix –carbaldehyde is added to the name of the ring. The carbon attached to this moiety will get the #1 location number in naming the ring. Aldehydes take their name Continue reading >>

Aldehydes And Ketones

Aldehydes And Ketones

Aldehydes and Ketones The connection between the structures of alkenes and alkanes was previously established, which noted that we can transform an alkene into an alkane by adding an H2 molecule across the C=C double bond. The driving force behind this reaction is the difference between the strengths of the bonds that must be broken and the bonds that form in the reaction. In the course of this hydrogenation reaction, a relatively strong HH bond (435 kJ/mol) and a moderately strong carbon-carbon bond (270 kJ/mol) are broken, but two strong CH bonds (439 kJ/mol) are formed. The reduction of an alkene to an alkane is therefore an exothermic reaction. What about the addition of an H2 molecule across a C=O double bond? Once again, a significant amount of energy has to be invested in this reaction to break the HH bond (435 kJ/mol) and the carbon-oxygen bond (375 kJ/mol). The overall reaction is still exothermic, however, because of the strength of the CH bond (439 kJ/mol) and the OH bond (498 kJ/mol) that are formed. The addition of hydrogen across a C=O double bond raises several important points. First, and perhaps foremost, it shows the connection between the chemistry of primary alcohols and aldehydes. But it also helps us understand the origin of the term aldehyde. If a reduction reaction in which H2 is added across a double bond is an example of a hydrogenation reaction, then an oxidation reaction in which an H2 molecule is removed to form a double bond might be called dehydrogenation. Thus, using the symbol [O] to represent an oxidizing agent, we see that the product of the oxidation of a primary alcohol is literally an "al-dehyd" or aldehyde. It is an alcohol that has been dehydrogenated. This reaction also illustrates the importance of differentiating between primar Continue reading >>

Aldehydes And Ketones

Aldehydes And Ketones

Can you resist the smell of a fresh baked cinnamon bun? There’s nothing like the smell of a fresh cinnamon roll. The taste is even better. But what causes that delicious taste? This flavoring comes from the bark of a tree (actually, several different kinds of trees). One of the major compounds responsible for the taste and odor of cinnamon is cinnamaldehyde. Cinnamon has been widely used throughout the centuries to treat a number of different disorders. In ancient times, doctors believed it could cure snakebite poisoning, freckles, and the common cold. Today there are several research studies being carried out on the health benefits of cinnamon. So, enjoy that cinnamon roll – it just might be good for you. Aldehydes and Ketones Aldehydes and ketones are two related categories of organic compounds that both contain the carbonyl group, shown below. The difference between aldehydes and ketones is the placement of the carbonyl group within the molecule. An aldehyde is an organic compound in which the carbonyl group is attached to a carbon atom at the end of a carbon chain. A ketone is an organic compound in which the carbonyl group is attached to a carbon atom within the carbon chain. The general formulas for each are shown below. For aldehydes, the R group may be a hydrogen atom or any length carbon chain. Aldehydes are named by finding the longest continuous chain that contains the carbonyl group. Change the –e at the end of the name of the alkane to –al. For ketones, R and R’ must be carbon chains, of either the same or different lengths. The steps for naming ketones, followed by two examples, are shown below. Name the parent compound by finding the longest continuous chain that contains the carbonyl group. Change the –e at the end of the name of the alkane t Continue reading >>

1. Nomenclature Of Aldehydes And Ketones

1. Nomenclature Of Aldehydes And Ketones

Aldehydes and ketones are organic compounds which incorporate a carbonyl functional group, C=O. The carbon atom of this group has two remaining bonds that may be occupied by hydrogen or alkyl or aryl substituents. If at least one of these substituents is hydrogen, the compound is an aldehyde. If neither is hydrogen, the compound is a ketone. The IUPAC system of nomenclature assigns a characteristic suffix to these classes, al to aldehydes and one to ketones. For example, H2C=O is methanal, more commonly called formaldehyde. Since an aldehyde carbonyl group must always lie at the end of a carbon chain, it is by default position #1, and therefore defines the numbering direction. A ketone carbonyl function may be located anywhere within a chain or ring, and its position is given by a locator number. Chain numbering normally starts from the end nearest the carbonyl group. In cyclic ketones the carbonyl group is assigned position #1, and this number is not cited in the name, unless more than one carbonyl group is present. If you are uncertain about the IUPAC rules for nomenclature you should review them now. Examples of IUPAC names are provided (in blue) in the following diagram. Common names are in red, and derived names in black. In common names carbon atoms near the carbonyl group are often designated by Greek letters. The atom adjacent to the function is alpha, the next removed is beta and so on. Since ketones have two sets of neighboring atoms, one set is labeled α, β etc., and the other α', β' etc. Very simple ketones, such as propanone and phenylethanone (first two examples in the right column), do not require a locator number, since there is only one possible site for a ketone carbonyl function. Likewise, locator numbers are omitted for the simple dialdehyde at t Continue reading >>

Aldehyde

Aldehyde

Aldehyde, any of a class of organic compounds, in which a carbon atom shares a double bond with an oxygen atom, a single bond with a hydrogen atom, and a single bond with another atom or group of atoms (designated R in general chemical formulas and structure diagrams). The double bond between carbon and oxygen is characteristic of all aldehydes and is known as the carbonyl group. Many aldehydes have pleasant odours, and in principle, they are derived from alcohols by dehydrogenation (removal of hydrogen), from which process came the name aldehyde. Aldehydes undergo a wide variety of chemical reactions, including polymerization. Their combination with other types of molecules produces the so-called aldehyde condensation polymers, which have been used in plastics such as Bakelite and in the laminate tabletop material Formica. Aldehydes are also useful as solvents and perfume ingredients and as intermediates in the production of dyes and pharmaceuticals. Certain aldehydes are involved in physiological processes. Examples are retinal (vitamin A aldehyde), important in human vision, and pyridoxal phosphate, one of the forms of vitamin B6. Glucose and other so-called reducing sugars are aldehydes, as are several natural and synthetic hormones. Structure of aldehydes In formaldehyde, the simplest aldehyde, the carbonyl group is bonded to two hydrogen atoms. In all other aldehydes, the carbonyl group is bonded to one hydrogen and one carbon group. In condensed structural formulas, the carbonyl group of an aldehyde is commonly represented as −CHO. Using this convention, the formula of formaldehyde is HCHO and that of acetaldehyde is CH3CHO. The carbon atoms bonded to the carbonyl group of an aldehyde may be part of saturated or unsaturated alkyl groups, or they may be alicycli Continue reading >>

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